1. Technical Field
The present invention relates generally to methods and devices for the measurement of the color of reflected and emitted light, and particularly to a handheld colorimeter.
2. Description of Related Art
Many fields of endeavor require quick accurate measure of the color of objects, or a comparison between objects. In addition, there are many color blind people that have difficulty accurately judging colors to varying degrees. There are also people who may not be color blind, but have simply not learned all of the subtle color variations and names. When these people read books, work on a computer, shop for clothes, etc., they may not always be able to tell the color of the objects at which they are looking.
Currently, handheld colorimeters are available for measuring the color of an object. These devices measure color by placing the tip of the probe against (or in close proximity to) the surface of the object being measured. The colorimeter generates a single measurement from three data points representing the reflectance of the three primary colors red, green, and blue (RGB). The single color value can then be compared to a preloaded table of color values.
However, current handheld colorimeters have several limitations. Current colorimeters cannot measure color at a distance and have problems handling ambient light. Current methods also have problems with changes in the intensity of artificial lights, such as florescent lights. In addition, the prior art requires recalibration by the user upon every use.
Therefore, it would be desirable to have a handheld colorimeter that can measure the color of distant objects and can properly compensate for ambient light, without the need for constant recalibration.
The present invention provides a handheld, pen-like colorimeter for measuring the color of an object. The invention comprising three light sensors, each of which detects a separate primary color. A microprocessor in the colorimeter calculates a single composite color value from the three separate color measurements from the light sensors and then compares the composite color value with a list of color values, wherein each value corresponds to a unique color name. The colorimeter selects the color name that matches the composite color value of the object and presents the color name to a user, by means of a liquid crystal display (LCD) or an audio speaker.
When the sensors use ambient light to measure the color, a compensation must be made for the coloration of the ambient light. The ambient light is also measured and a white balance measurement is used to correct for the coloration of the light source(s), as is typically done in video cameras and other such devices.
Another embodiment of the present invention uses lasers emitting primary colors, in addition to passive light sensors. The lasers shine on an object one at a time or simultaneously, and the reflected laser light from the three lasers is detected by one or more special telephoto light sensor(s). The three color measurements are then combined to produce a composite value, similar to the first embodiment. The lasers can focus on a very small or larger areas at a distance, permitting color measurements in situations where it may not be convenient to bring the measuring device within close range of the object surface being measured.